In a significant expansion of the war on drugs, the United States has begun training an elite unit of counter-narcotics police in Ghana and plans similar units in Nigeria and Kenya.

It is part of an effort to combat the Latin American trafficking organisations that are increasingly using Africa to smuggle cocaine into Europe.

The growing US involvement in Africa follows an earlier effort in Central America.

In both regions, the US is responding to fears that crackdowns in more direct staging points for smuggling have prompted traffickers to move into smaller and weakly governed states.

In May, William Brownfield, the Assistant Secretary of State for international narcotics and law enforcement, travelled to Ghana and Liberia to put the finishing touches on a west Africa ”co-operatives security initiative”, which will try to replicate across 15 nations the steps taken in Central America and Mexico.

But Bruce Bagley, a professor at the University of Miami, said what had happened in west Africa over the past few years was the latest example of the ”whack-a-mole” problem, in which making trafficking more difficult in one place simply shifts it to another.

”As they put on the pressure, they are going to detour routes, but they are not going to stop the flow,” he said. ”And there is always a blowback to this. You start killing people in foreign countries – whether criminals or not – and there is going to be fallout.”

William Wechsler, the Pentagon’s top counter-narcotics officer, said that observing drug traffickers’ advances into west Africa – and the response from US and local authorities – was like watching a rerun of the drug war in the western hemisphere